Pitch detectors are used for a wide range of applications including, for instance, Speech compression (coding), Speech Synthesis, such as speech reconstruction from speech recognition features, and others.
There are known in the art various techniques of pitch detectors, e.g.,
Y. Medan, E. Yair, D. Chazan, Super Resolution Pitch Determination for Speech Signals, IEEE ASSP vol 39 pp 40-48, 1991.
Pitch detectors tend to find in certain occasions integer multiples or integer fractions of the pitch. Most often the reason for this is due to a rapid change of pitch or a transition between two sounds as well as the existence of a raspy or hoarse sound all of which mar the regular structure of the spectrum. The result of this marring is the creation of additional spectral lines which are often at multiples of half the pitch frequency, but one third and one quarter frequencies can occur too. When such additional lines are missed, a multiple of the pitch frequency is found. When they are incorrectly counted a fraction of the pitch frequency is detected.
Applications, such as Speech compression, which use the specified marred pitch signal will manifest degraded performance.
There is accordingly a need in the art to provide for a technique for smoothing marred pitch values in a detected pitch signal.
Related art include:
Robust pitch estimation using an event based adaptive Gaussian derivative filter Shah, A.; Ramachandran, R. P.; Lewis, M. A. Circuits and Systems, 2002. ISCAS 2002. IEEE International Symposium on, 2002. Page(s):II-843-II-846 vol. 2. which aims at finding pitch in noisy speech.